In the first chapters of Lore of Running, exercise physiologist, runner, and author Timothy Noakes, MD, suggests that serious running and endurance efforts are arguably, according to the reasoning of standard exercise science, a death defying activity—except that, on second look, endurance athletes actually have an almost perfect safety net. According to the standard model of strenuous exercise and the circulation of oxygen that has dominated research and training for the last century, the heart, which pumps oxygen to the muscles, should in fact run out of energy before the skeletal muscles do. As oxygen becomes scarce for the skeletal muscles, they shift to the energy process which burns carbohydrate and utilizes lactate. But the heart, as it turns out, is not a lactate muscle; it runs only on oxygen. So the heart should beat harder and harder just to supply itself with oxygen. When oxygen becomes scarce and muscles switch to lactate energy, the heart should run out of energy before the muscles—a dangerous proposition.
Noakes reasons that, according to this standard model of exercise physiology, many healthy runners should find themselves running until they feel a pain in their chests—fatigue of the heart and angina pectoris. But they don’t. Somehow the skeletal muscles of these runners fatigue and shut down before the heart itself runs out of oxygen and is damaged.
The runner’s body, as it turns out, has mechanisms for dealing with other potentially catastrophic events when it comes to temperature regulation, for example, or low glycogen levels in the blood or liver.
Lore of Running, divided into four sections, is at least two different books. This blog post will review what might be called the first book. The first four chapters, 255 pages out of 930 pages total, are research reviews of a century of scientific literature from exercise physiology as it applies to running and endurance training. These pages are a dense read.
Noakes begins with a chapter that describes the structure and functions of the muscles, including explanations of how muscles contract and fire and how type one slow twitch muscles are different from type two fast twitch muscles. A chapter on “Oxygen Transport and Running Economy” evaluates what might be called the VO2 max theory of training, which focuses on optimizing the amount of oxygen the cardiovascular system can circulate and its impact on performance. Noakes suggests alternatively that training actually seems to improve performance mainly by improving running economy, like promoting physiological adaptations that allow the body to use its available oxygen and other energy resources more efficiently to run faster and farther. A third chapter on energy systems considers matters like diet for runners, presenting scientific research about the body’s use of fats, carbohydrates, and proteins during exercise. Finally, the last scientific chapter outlines the ways that the body regulates temperature during exercise, explaining what happens in situations like dehydration and heat exhaustion.
As he explains the science of exercise and running and weaves together information from scientific research, Noakes takes aim at some of the fundamental ideas that have driven training programs for the last fifty years.
All the way back in 1923, Noakes explains, the pioneering researchers A.V. Hill , later a Nobel Laureate, and Hartley Lupton were among the first to measure oxygen consumption during exercise and to speculate on the role of oxygen as a determinant of athletic ability. At low exercise levels, energy comes from aerobic (oxygen-requiring) sources, connected to adenosine triphosphate (ATP) production in the mitochondria of the skeletal muscles. When humans wanted to run faster than 13 kilometers per hour, according to Hill and Lupton, a secondary energy source was provided by anaerobic (meaning in the absence of oxygen) metabolism. Later researchers built upon this research to develop a more individualized concept of VO2 max, including the idea that individuals could improve that VO2 max to improve performance. Others used the basic notions of Hill and Lupton to develop the anaerobic threshold idea. In the path from aerobic to anaerobic, shortly before an athlete reached maximum work rate, oxygen consumption reached a plateau and did not increase further—the so-called anaerobic threshold. Improving VO2 max and raising the anaerobic threshold in athletes has been the stated goal of endurance training programs for the last fifty years.
Noakes proceeds to revise these theories. While good runners have a high VO2 max, and poor runners do not, the athletes with the highest VO2 max are not necessarily the best performers. Something else must be involved in performance other than the heart’s capacity to pump the maximum amount of oxygen at maximum effort. Noakes also disputes the idea that an anaerobic or lactate threshold—a set point in all runners where muscles shift from oxygen energy to burning carbohydrates to produce lactate as a form of muscle fuel—even exists.
Noakes’s revisions are not dramatic. VO2 max, the capacity to transport larger amounts of oxygen to the muscles at maximum effort, Noakes suggests, may be less important to endurance athletes than the efficiency with which the body uses available energy resources, including oxygen, at lower levels—like 80 percent of maximum effort. In terms of the anaerobic threshold, it is technically a misunderstanding to say that muscles switch at a set point from aerobic to anaerobic activity. Muscles produce lactate from the very beginning of exercise, it turns out, but levels are not clearly evident until exercise intensity increases. Even if a lactate threshold does not exist, Noakes uses the term lactate turnpoint—a point at which blood levels of lactate show a significant and visible increase. At 85 to 95 percent of VO2 max efforts, virtually all of the energy in the skeletal muscles comes from carbohydrate oxidation and the production of lactate.
In the middle of these scientific discussions, Noakes characteristically drops powerful pieces of practical information for coaches. In terms of raising the lactate turnpoint as a goal of training, research suggests that improvement happens quickly. In one study, athletes training for a marathon by running 73 kilometers per week (just under 45 miles) over 36 weeks improved their lactate turnpoints from 63 percent of VO2 max to 71 percent of VO2 max. But all of that change took place in the first 12 weeks of training, and they did not improve after that. What’s more, other studies suggest that more than half of that improvement actually takes place in the first 10.5 days of training. If training to improve the lactate turnpoint is a goal, training specifically for that goal, it would seem, should last for approximately the first 12 weeks of a training program—with an emphasis on the first weeks.
Moreover, this raises another puzzle: How is it then that runners improve after 12 weeks?
Noakes presents scientific information on other topics in these chapters, and some of it is very practical, as well. In the muscle function chapter, he notes that the scientific evidence is not clear about the value of weight training for endurance athletes. Running economy is not just training to use oxygen economically, but it includes the benefits of lighter shoes, properly fitting clothes, and even short hair. He presents the historical research on carbohydrate loading in the energy systems chapter. He notes that the science of temperature regulation predicts that the winners of Olympic marathons run in severe summer heat will be smaller runners like Josian Thugwane in the 1996 Atlanta marathon.
But Noakes is developing an argument in these chapters. As Noakes presents his well-reasoned and researched array of information explaining the “Cardiovascular/Anaerobic Model” of exercise physiology which has been the paradigm for over fifty years, a mystery emerges. It is the mystery of that safety net– my term, not Noakes’s. Noakes writes: “The major weakness of the Cardiovascular/Anaerobic Model is that it predicts something that does not occur: the heart does not fatigue as a result of anaerobsis during maximal exercise, nor do healthy subjects terminate exercise because they develop chest pain (angina pectoris) resulting from an inadequate oxygen supply to the heart. Thus, proponents of this model face the challenge of explaining how blood supply to the exercising skeletal muscles can be inadequate while that to the heart is adequate…” (32).
To solve the mystery, Noakes goes all the way back to Hill and Lupton and looks at their original findings, which, though flawed, still hold riches. Hill and Lupton, Noakes suggests, speculated about something that was forgotten for almost 80 years. Hill and Lupton understood that it would be useless and dangerous for the heart to continue beating harder and harder to supply itself with oxygen. “They suggested that there was a mechanism in the body (either in the heart muscle or in the nervous system) that caused a slowing of the circulation as soon as a serious degree of unsaturation occurred, and vice versa,” Noakes writes “This mechanism, they said, acted as a governor” (32).
The big words that Noakes uses to name this idea are the Integrated Neuromuscular Recruitment Model of Exercise—or in short, as he calls it, “the Central Governor Model.” The heart is the organ at greatest risk during exercise—and yet in healthy athletes, it always survives. Noakes writes: “Thus, a mechanism must exist to restrain the overvigorous use of the exercising skeletal muscles, which would imperil the heart” (34). Something measures the oxygenation of the heart, and perhaps the brain, as well, and when dangerous conditions approach, sends out signals to stop recruiting the work of the muscles creating the overload. As a result, “the body experiences fatigue. Note that, like pain, fatigue is always sensed exclusively by the brain” (34). Then the work output of the muscles and the heart falls, so the heart needs less oxygen, thereby protecting the heart from the damage of oxygen starvation.
Noakes approaches this same speculative territory about a Central Governor at several points in these early chapters. He gets there in these chapters, always, by this scientific, carefully reasoned approach. The Central Governor doesn’t just monitor oxygenation of the blood, it would seem, but also body temperature, and blood glucose levels, and glycogen levels in the liver, and many other variables that put us in potential danger when we exercise at stressful levels.
Noakes and his colleague St. Clair Gibson have suggested a different definition of fatigue: “fatigue is actually a central (brain) perception, in fact a sensation or emotion and not a direct physical event” (147). And in terms of runners and fatigue, Noakes has added this contribution: “fatigue is merely the physical manifestation of a change in pacing strategy” (147).
However scientific the route that Noakes takes to present his idea, the Central Governor idea has rich implications that are both philosophical and practical. I can’t imagine that I am the first coach for whom the Central Governor idea seemed to spring from the page with a life of its own.
The implication of what Noakes suggests, with or without research to back it up, is what most coaches probably already know. We really aren’t training athletes so that they have a higher VO2 max or higher lactate threshold. We’re really training their Central Governors, some mechanism of brain function, so that their brains allow their bodies to work a little bit harder before their brains decide to shut them down—or slow them down. Alternatively, in very practical terms, proper pacing keeps the Central Governor happy so that it doesn’t sense any danger—and the runner does not feel fatigue.
As coaches often tell their athletes: “It is all in your head.” Or, “Success in running is 90 percent mental.” Or simply, “You have to believe you can do it.”
I post on our team bulletin board late in each track season a quote by United States Olympic bronze medalist at 10,000 meters Lynn Jennings: “Mental will is a muscle that needs exercise, just like the muscles of the body.” Or as Olympic marathoner and writer Kenny Moore puts it, in a quote from a book my team gave me at the end of track season this year, “It is the illusion that we can go no faster that holds us back.”
Of course it is more complicated than this. But that simple notion that our athletes have to believe they can do something seems to be proof that some kind of Central Governor is operating.